In general, all electronic equipment largely uses a voltage regulator module (VRM), such as a low drop-out (LDO) or a switching mode power supply (SMPS) to receive stable power supply voltage. However, the existing analog control method of VRM is complicated in design and has a limited range of application, which causes additional time and cost for developing the VRM. As an attempt to remove these shortcomings, recent studies have been largely conducted on a digital control based SMPS that does not require a large number of components except for an LC filter and a small number of discrete elements used to adjust an external output.
The digital SMPS has a superior immunity to changes in the power supply noise while ensuring superior steady-state and dynamic performance, and thus is implemented more easily than the analog SMPS. However, the digital SMPS requires a high operating frequency in order to improve the precision (resolution) of a digital pulse width modulator (DPWM) for stabilizing an output voltage. In order to reduce such a shortcoming, many studies have been conducted on a counter based DPWM, a delay line based DPWM and a hybrid DPWM. However, these DPWMs require a high operating frequency (high power) and a large surface area in order to ensure a high resolution duty ratio.
In order to remove the shortcomings of the DPWM controlled SMPS described above, recent studies have been conducted on delta-sigma (Σ-Δ) modulator schemes that operate at a low-power and high-frequency. However, these delta-sigma (Σ-Δ) modulator schemes use analog-digital converters (ADC) and thus are sensitive to influence from power supply voltage noise and noise distortion filter coefficients, thus having significantly low ADC performance. In addition, the delta-sigma (Σ-Δ) modulator schemes have a narrow voltage control loop bandwidth, and thus dynamic response characteristics need to be improved.
As a relevant technology, Korean Patent Publication No. 10-2010-0051881 (a switching mode power supply and method) discloses a switching mode power supply and a method thereof capable of stabilizing a voltage output from an SMPS circuit to prevent the system performance from being lowered due to increase in an output voltage ripple with a load change. In order to stabilize a voltage output from an SMPS circuit, information related to future load change is received and sampled, and in this case a digital pulse width modulator not using a switch-capacitor delay scheme is applied.
Korean Patent Publication No. 10-2009-0051143 (a self-calibration digital pulse-width modulator) discloses a hybrid type DPWM for stabilizing the switching frequency by enhancing the efficiency of a digitally controlled SMPS circuit. However, the hybrid type DPWM, by its nature, requires a high operating frequency (high power) and a large surface area for a high resolution duty ratio.